CREATING A CUSTOMIZED

BOOT CD/DVD FOR THE

SOLARIS™ OPERATING
SYSTEM FOR X86 PLATFORMS
John Cecere, Sun Services
Dana Fagerstrom, Sun Services
Sun BluePrints™ OnLine — December 2005

Part No 819-3731-10
Revision 1.0, 11/29/05
Edition: December 2005
© 2005 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, CA 95054 USA

All rights reserved.

This product or document is protected by copyright and distributed under licenses restricting its use, copying, distribution, and decompilation.
No part of this product or document may be reproduced in any form by any means without prior written authorization of Sun and its licensors,
if any. Third-party software, including font technology, is copyrighted and licensed from Sun suppliers.

Parts of the product may be derived from Berkeley BSD systems, licensed from the University of California.

Sun, Sun Microsystems, the Sun logo, Solaris, Solaris JumpStart, and Sun BluePrints are trademarks, registered trademarks, or service marks
of Sun Microsystems, Inc. in the U.S. and other countries.

UNIX is a registered trademark in the United States and other countries, exclusively licensed through X/Open Company, Ltd.

All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. in the U.S. and other
countries. Products bearing SPARC trademarks are based upon an architecture developed by Sun Microsystems, Inc.

The OPEN LOOK and Sun™ Graphical User Interface was developed by Sun Microsystems, Inc. for its users and licensees. Sun
acknowledges the pioneering efforts of Xerox in researching and developing the concept of visual or graphical user interfaces for the computer
industry. Sun holds a non-exclusive license from Xerox to the Xerox Graphical User Interface, which license also covers Sun’s licensees who
implement OPEN LOOK GUIs and otherwise comply with Sun’s written license agreements.

RESTRICTED RIGHTS: Use, duplication, or disclosure by the U.S. Government is subject to restrictions of FAR 52.227-14(g)(2)(6/87) and
FAR 52.227-19(6/87), or DFAR 252.227-7015(b)(6/95) and DFAR 227.7202-3(a). DOCUMENTATION IS PROVIDED “AS IS” AND ALL
EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE DISCLAIMED, EXCEPT TO THE EXTENT
THAT SUCH DISCLAIMERS HELD TO BE LEGALLY INVALID.

Please
Recycle
 Sun Microsystems, Inc.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms. . . . . . . . . 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
A New Boot Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Disk Layout (Hard Disk). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Partition Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Solaris Disk Device Paths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
fdisk Master Boot Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
mboot, pboot, and bootblk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Solaris System VTOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Disk Layout (CDROM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
El Torito . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
fdisk on CDROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Solaris System VTOC on CDROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Steps for Creating a Customized Solaris on x86 Boot CD/DVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Step 1: Create an ISO9660 File System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Step 2: Create a Solaris Miniroot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Step 3: Create the Boot Files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Step 4: Create the Composite ISO CD Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
References and Related Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
About the Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
John Cecere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Dana Fagerstrom. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Ordering Sun Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Accessing Sun Documentation Online . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
1-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

Creating a Customized Boot CD/DVD for the Solaris™

Operating System for x86 Platforms

This Sun BluePrints™ Online article provides all the information necessary to create a customized boot
CD/DVD for the SolarisTM Operating System for x86 Platforms (Solaris on x86). This article consists of the
following sections:

• Introduction
• A New Boot Architecture
• Disk Layout (Hard Disk)
• Disk Layout (CDROM)
• Steps for Creating a Customized Solaris on x86 Boot CD/DVD
• Conclusion
• References and Related Sources
• About the Authors
• Ordering Sun Documents
• Accessing Sun Documentation Online

Note – Unless otherwise noted, this article makes no distinction between a CD or DVD. Because the file
systems and layout used are the same, a DVD in the context of this article is just a CD with a lot more
space (4.7GB versus 650MB) available. Because of this, the terms CD and CDROM can be used
interchangeably with DVD in this article.

Introduction
This purpose of this article is to explain the mechanics of the Solaris on x86 boot process so that you
understand what is needed to create a customized CD. It explains both the hard disk and CD boot
processes, and points out the differences between the two.

There are a number of practical applications for this topic:

• Solaris JumpStartTM software—The feature in Solaris that allows access to Solaris installation media and
configuration rules over a network.
• Diagnostics—The ability to create a bootable CD for the purpose of diagnosing system problems without
accessing or modifying the copy of the operating system that is installed on the target system.
• Restoration—The ability to create a bootable CD with tools that aid in the repair and restoration of a
down system.
• Diskless clients that cannot do PXE booting—PXE is a DHCP-based network-based installation
technology similar to Solaris Jumpstart software. Some older x86-based systems are incapable of using
PXE.
• Canned Firewall—The creation of a bootable CD that starts Solaris on a system configured with multiple
network interfaces. A preset ipf configuration is then used to establish a network firewall on that system.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
2-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

The following topics are outside the scope of this article: X86BOOT boot partition (refer to http://www.ata-
atapi.com/hiwmbr.htm), floppy disk booting (refer to http://www.ata-atapi.com/hiwdos.htm), PXE booting
(refer to http://docs.sun.com/app/docs/doc/817-5504/6mkv4nh8g?a=view), and booting other (non-
Solaris) operating systems.

Information on Solaris JumpStart software has also been intentionally left out of this article because a
wealth of available information already exists, including several Sun Blueprints documents described in
“References and Related Sources” on page 14. For more information about Solaris JumpStart software,
refer to: http://docs.sun.com/app/docs/doc/817-5506/6mkv6ki5q?q=jumpstart&a=view

This article begins by examining the layout of a hard disk in the x86 architecture and the components on it
that are used for booting. It then describes the pieces that are unique to a CD boot. Finally, this article puts
the pieces together and creates an image file that can be burned to CD.

A New Boot Architecture

As described in Jan Setje-Eilers's blog (see http://blogs.sun.com/roller/page/
setje?entry=a_new_boot_architecture), there are current plans to provide a new boot architecture for
Solaris on x86 that will use the open source GRUB (GRand Unified Bootloader, see http://www.gnu.org/
software/grub/) as the bootloader in place of the Device Configuration Assistant (DCA). The planned initial
delivery is based on GRUB version 0.95, and would be updated as newer versions come out. Unlike Linux
and FreeBSD, the Solaris kernel would be fully compliant with the Multiboot Specification
(http://www.gnu.org/software/grub/manual/multiboot/). Hence, Solaris could be booted via any bootloader
that implements the Multiboot Specification.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
3-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

Disk Layout (Hard Disk)

The following figure shows the layout of a Solaris on x86 hard disk.

Sector
0
FDISK Master Boot Record
63 (track 1)
pboot
64
Solaris VTOC 66
Boot block
First sector of cylinder 1
Root filesystem

c0t0d0s0

c0t0d0p0

c0t0d0p1

c0t0d0s2

swap

c0t0d0s1

Figure 1. Hard Disk Layout

This figure assumes that the boot drive is c0t0d0, that the Solaris OS is the only operating system
installed, and that it uses the entire disk. In the example shown in the figure above, Solaris is installed with
a single (root) file system and a swap partition.

Partition Structures
The first thing to understand about the layout of a Solaris on x86 boot disk is that there are two different
partition structures within it:

• The standard x86 architecture partitioning scheme, commonly referred to as fdisk.

• The Solaris Volume Table of Contents (VTOC). The VTOC is actually embedded within an fdisk
partition. From the perspective of the VTOC, the first fdisk partition that has a Solaris system type
(0x82 or 0xbf) in fdisk is seen as the whole disk, which has the effect of creating a sort of virtual disk
from an fdisk partition. This design allows Solaris on x86 to coexist with other operating systems that
use fdisk.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
4-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

The fdisk Master Boot Record is a key component. The installation process installs the program known
as mboot into the first 446 bytes of this sector. The next 64 bytes is the fdisk partition table, which is
capable of holding information for four partitions. The last 2 bytes contain the signature 0xAA55.
This signature must be set; otherwise, the MBR is considered corrupt by the BIOS and will not be used.

In Figure 1, the one and only partition starts at sector 63 (LBA track boundary). The first sector of the
partition contains the Solaris partition boot (pboot). The installboot program is responsible for placing
these two components after the first sector according to the following rules:

• The /usr/platform/i86pc/lib/fs/ufs/pboot file is copied first, and is exactly 1 sector long.

• The pboot file is followed by 2 sectors that are allocated for the Solaris system VTOC.
The installboot skips over this.
• The boot block (bootblk) follows immediately after the VTOC space.
The /usr/platform/i86pc/lib/fs/ufs/bootblk file is copied here.

The cylinder following the bootblk is typically where the root file system starts.

The following table describes the resulting layout.

Table 1. Boot Components Layout

Component Start Length Contents

• Bytes 0-445: Boot code
fdisk Master (/usr/lib/fs/ufs/mboot)
sector 0 of the disk 1 sector
Boot Record • Bytes 446-509: partition table
• Bytes 510-511: Signature 0xaa55
pboot (partition 1st sector of fdisk 1 sector /usr/platform/i86pc/lib/fs/ufs/pboot
boot) partition
Solaris system 2nd sector of fdisk
VTOC 2 sectors Disk label, Volume Table of Contents
partition
4th sector of fdisk Can occupy up to the /usr/platform/i86pc/lib/fs/ufs/bootblk
Boot block partition end of the first cylinder
Beginning of the first Up to 2 cylinders
VTOC partition cylinder after the before the end of the File systems, swap, raw devices, and so on.
space boot block fdisk partition

Solaris Disk Device Paths

In Solaris on SPARC, where VTOC is the only partitioning scheme used, the partitions (or slices) are
referred to by the “s” value in the device path. For example, /dev/dsk/c0t0d0s0 refers to the first
partition on the disk. This does not change for Solaris on x86, but because it has a second partitioning
scheme in which the VTOC is embedded, some differences need to be clarified. Normally, slice 2 refers to
the entire disk in Solaris on SPARC. In Solaris on x86, however, slice 2 refers to everything on the disk that
can be addressed using the Solaris system VTOC structure—the entire fdisk partition on which Solaris
on x86 resides, minus the last two cylinders.1

1.These two cylinders were previously used for alternate cylinders but are no longer used as such in Solaris 10.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
5-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

Solaris on x86 also has device path names, described in the following table, to handle access to the
fdisk structure of a disk.

Table 2. fdisk Solaris Device Path Names

Component Solaris Device Paths

Entire Physical Disk /dev/dsk/c0t0d0p0, /dev/rdsk/c0t0d0p0
fdisk partition 1 /dev/dsk/c0t0d0p1, /dev/rdsk/c0t0d0p1
fdisk partition 2 /dev/dsk/c0t0d0p2, /dev/rdsk/c0t0d0p2
fdisk partition 3 /dev/dsk/c0t0d0p3, /dev/rdsk/c0t0d0p3
fdisk partition 4 /dev/dsk/c0t0d0p4, /dev/rdsk/c0t0d0p4

For both Solaris on x86 and Solaris on SPARC, the device names given to SCSI disks use the cXtYdZs#
(controller,target,device,slice) convention. However, Solaris on x86 systems typically come with ATA
(Advanced Technology Attachment) controllers and disks. ATA does not use the concept of targets, and a
controller is capable of addressing only up to four devices. The following table shows the mapping of
devices on an ATA controller to Solaris device paths.2

Table 3. ATA Device Path Names

Function Solaris Device Paths

Primary Master /dev/rdsk/c0d0p0, /dev/dsk/c0d0p0
Primary Slave /dev/rdsk/c0d1p0, /dev/dsk/c0d1p0
Secondary Master /dev/rdsk/c1d0p0, /dev/dsk/c1d0p0
Secondary Slave /dev/rdsk/c1d1p0, /dev/dsk/c1d1p0

fdisk Master Boot Record

In addition to understanding Solaris OS disk device paths, it is useful to understand the structure of fdisk.
The first 512 bytes of any disk in the x86 architecture comprise what is commonly called the Master Boot
Record. This sector contains the initial boot code for booting an operating system. In Solaris on x86, this
program is called mboot. The function of mboot is to locate the active partition, then load and execute a
program contained in sector 0 of that partition. In the case of Solaris, this is the program pboot.

The MBR also contains the fdisk partition table. As will be described later in this article, the fdisk
partition table needs to manipulated to create a bootable CD/DVD. The partition table contains four 16-byte
entries, one for each possible primary partition.3

Out of these 16 bytes, the following fields have impact on the boot process: the active flag, system type,
relative sector, and the number of sectors.

2.Unlike Solaris on x86, ATA device paths in Solaris on SPARC are given target IDs.
3.Solaris on x86 does not currently support extended partitions.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
6-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

• The active flag field denotes whether this partition is the boot partition. It can contain the value 0 (not a
boot partition) or 0x80 (boot partition). The mboot program looks for the first partition on the disk with
this flag set to 0x80, and then attempts to boot from it.
• The system type field contains a 1-byte tag that identifies what the partition is being used for. No
standards body has defined values for this tag. As a result, cases exist in which a specific value has
more than one meaning, as is true for Solaris on x86. Prior to Solaris 10, Solaris partitions had a type of
0x82, which also happened to be the type of a Linux swap partition. This conflict caused problems when
installing both operating systems on a single disk, because each OS wanted to use the partition tagged
with 0x82 for its own purpose. With the release of Solaris 10, Sun has officially changed the partition
type code to 0xbf (decimal 191). For more information about the values used for x86 partition types,
refer to the following document:
http://www.win.tue.nl/~aeb/partitions/partition_types-1.html

• The fdisk partition table also contains information about the starting sector and size of the partitions.
Later in this article, these values will be calculated, based on the size of input files, to create a bootable
CD/DVD.

mboot, pboot, and bootblk

These three components of the disk actually exist as files within the file system structure of Solaris on x86.
However, because they cannot exist in any random location, they need to be transferred to specific sectors
of the disk (for example, via dd) in order for the boot process to function properly. They essentially make
up what are called the stage0 (mboot and pboot) and stage1 (bootblk) steps of the boot process.

As mentioned previously, the mboot (master boot) program is responsible for locating the first fdisk
partition that contains a bootable/active flag. It then loads the first sector from that partition and executes it.
In the case of Solaris on x86, the first sector of this partition contains the pboot (partition boot) program.
The job of the pboot program is to locate the boot block (bootblk) within the partition, then load and
execute it. As shown in Figure 1, the boot block program is always located directly after the VTOC, which is
two sectors long and starts directly after the pboot. The bootblk will then run the Device Configuration
Assistant (DCA), which will in turn load the kernel. As mentioned previously in this article, plans exist for a
future version of the Solaris OS to introduce a new boot architecture in which the bootblk will load GRUB
(GRand Unified Bootloader) instead of the DCA, and will use GRUB to load the kernel and kernel modules
instead.

Solaris System VTOC

In Solaris on SPARC, the layout of a hard disk is defined by the VTOC. Disk space is addressed in 512-
byte chunks of data called blocks. The VTOC is on the first block of the partition. Unlike an fdisk defined
partition, no boot code exists on the first block, only the VTOC information. The boot code, referred to as
the boot block, is contained in blocks 1-15.

The structure of the VTOC in Solaris on x86 is slightly different from its SPARC processor counterpart. The
VTOC for Solaris on x86 is able to accommodate 16 partitions, not just 8. This might not be immediately
evident, as the format command does not currently provide the capability to manipulate partitions 8-15,

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
7-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

but prtvtoc and fmthard do. The other difference in Solaris on x86 is that there are two sectors (instead
of just one) allocated for the VTOC.

The VTOC contains information about the size, location, and type of partitions on the disk, along with
information about the disk's geometry. When a CD/DVD image is created, this information gets generated
based on the file sizes of the miniroot and ISO image.

Disk Layout (CDROM)

The following figure shows the layout of a Solaris on x86 CDROM.

Sector
0
FDISK Master Boot Record
1
pboot.cd 2
Solaris VTOC
4
s8
Boot block
68 (CD sector 17)
El Torito

640 (CD cylinder 1)

ISO 9660 Filesystem
s1

p0

p1 & s2

Root Filesystem (miniroot)

s0

Figure 2. Solaris Disk Layout (CDROM)

The geometry of a CD is different from a hard disk in several ways.

• The sector size on a CDROM is defined as 2048 bytes, not 512. Even so, the tasks in this article work
mainly with 512-byte sector sizes, because this is what Solaris uses for the size of a disk block,
regardless of the medium.
• There is no concept of a head—a CDROM drive has only one head. Because of this, the track size and
cylinder size are the same—160 sectors (327680 bytes).

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
8-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

As with a hard disk, the CD uses mboot, pboot, and bootblk to boot. However, the mboot and pboot
programs differ slightly to account for the different sector size. The mboot and pboot files for a CD
(mboot.cd and pboot.cd) do not exist in the root file system of the CD and must be extracted from the
CD itself using the dd command.

The placement of pboot.cd, the VTOC, and the boot block differs slightly as well. Unlike a disk drive, they
are placed contiguously on the CD at the beginning, with each one starting at a 512-byte (disk block)
boundary.

El Torito
In addition to mboot.cd, pboot.cd, and bootblk, El Torito is the other boot component to consider with
a bootable CDROM. The El Torito specification for CDROM booting was designed by Phoenix
Technologies as a way to implement a bootable CDROM without needing to make drastic changes to the
BIOS. The El Torito information starts at CD sector 17 (2048*17 = byte 34816), which comes after the
bootblk, but before cylinder 1 of the CD, which is where an ISO 9660 file system is located.

El Torito specification defines:

• a boot catalog to allow multiple choices to boot from

• a boot record volume descriptor (brvd), which is a special volume descriptor on the CD to identify the
beginning of the boot catalog
• a validation entry as a means to check whether the boot catalog is a valid one
• an initial/default entry that describes what needs to be loaded

Other components of El Torito are not directly pertinent to the tasks described in this article.
The information needed to set up in El Torito for Solaris focuses on loading and executing the first 1024
bytes of the CD (mboot.cd and pboot.cd). For more information about El Torito, refer to:

http://www.phoenix.com/NR/rdonlyres/98D3219C-9CC9-4DF5-B496-A286D893E36A/0/specscdrom.pdf

fdisk on CDROM
The CD created using the instructions in “Steps for Creating a Customized Solaris on x86 Boot CD/DVD”
on page 9 (and on the standard Solaris on x86 boot CD) will have only one fdisk partition. This partition,
with the exception of the MBR, will span the entire disk and contain the VTOC structure.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
9-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

Solaris System VTOC on CDROM

The Solaris system VTOC on a standard Solaris on x86 boot CD defines four slices, as described in the
following table.

Table 4. VTOC Slices Defined on a Solaris on x86 Bootable CD

Partition VTOC tag Function

slice 0 root Root file system.
Placeholder for ISO9660 file system. This will encompass all of the
slice 1 unassigned sectors from the beginning of the VTOC addressable space to the
sector prior to the start of slice 0.
The entire CDROM, minus the MBR on the first sector. s2 and p1
slice 2 backup refer to the same area of the CDROM.
slice 8 boot Pointer to the boot information needed by Solaris.

Steps for Creating a Customized Solaris on x86 Boot CD/DVD

As shown in Figure 2, the CDROM image is really an ISO9660 file system with a Solaris UFS partition
placed immediately after it on the disk. Having the UFS appended in this way does not affect the ISO9660
file system itself. The ISO9660 file system ignores the presence of the UFS because its geometry is
specified within the ISO9660 volume descriptor table.

Having this structure makes it easy to create a copy of the CD. The dd command can be used to copy the
entire p0 device. The resulting image can be burned to CD with no modifications. This differs from Solaris
on SPARC, which uses the VTOC to define the geometry of the CD. With Solaris on SPARC, there are six
slices that all need to be copied separately, and then the slices need to be concatenated together as one
file to create a burnable image. If any modifications were made to any of the slices, padding must be added
to ensure that each slice starts on a CDROM cylinder boundary (327680 bytes).

To create a customized Solaris on x86 CD, complete the following steps:

• Step 1: Create an ISO9660 File System

• Step 2: Create a Solaris Miniroot
• Step 3: Create the Boot Files
• Step 4: Create the Composite ISO CD Image
The rest of this section describes how to perform these steps.

Step 1: Create an ISO9660 File System

On the standard Solaris on x86 1 of 2 boot CD, the ISO9660 file system contains (among other things)
installation packages, the network boot utilities (such as add_install_client), and Solaris JumpStart
software examples. Either keep whatever you want in this directory, or create an entirely new one with your
own content. The advantage of storing content here is that any operating system can read this file system
from the CD. This will not be true of the miniroot that will be created later.

In the simplest case, create a directory (such as /tmp/isodir):

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
10-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

# mkdir /tmp/isodir

You can populate this directory with anything you want. Consider storing files that need to be accessible
from any operating system. Remember that only Solaris systems will be able to access files in the miniroot
file system.

Step 2: Create a Solaris Miniroot

To boot Solaris on x86, begin by creating a root UFS file system, which you can get from a Solaris on x86
boot CD or DVD. The CD and DVD differ in this regard—the Solaris CD contains a single miniroot.
This miniroot is capable of being a root file system for a network boot client. Patches and packages can be
added to it. When the CD is inserted into a Solaris on x86 system running vold, this miniroot will be
accessible as s0.

The DVD contains two miniroots:

• The first miniroot also comes up in vold as s0, but is a very stripped down version of a root file system
and serves the sole function of being able to perform a Solaris installation (patches and packages
cannot be added to it).
• The second miniroot resides in the Solaris_10/Tools/Boot directory of the ISO file system (what
vold presents as s2). This is the equivalent of the s0 miniroot from the CDROM (patches and packages
can be added to it). For a customized boot CD, use either the second miniroot from the DVD or the
miniroot from the CD. Never use the s0 miniroot from the DVD!

To create a miniroot for use on a customized boot CD, start by creating an image file using the Solaris
lofiadm command. Begin by determining the desired size of the root file system, either by mounting the
root file system off of the Solaris on x86 CD (CD only), or by using du -sk in the DVD miniroot directory.

To see the size of the CD miniroot, insert the Solaris system CD in the drive of a Solaris on x86 system.4
The following examples assume that vold is running and always mounts a CD as /cdrom/cdrom0.
You should see two partitions from the CD—slice 0 and slice 2. Slice 0 is the slice that contains the root file
system.

# df -kl
Filesystem kbytes used avail capacity Mounted on
/dev/dsk/c0d0s0 10867092 8382503 2375919 78% /
/devices 0 0 0 0% /devices

<snip>

/vol/dev/dsk/c1t1d0/sol_10_305_x86/s2
219744 219744 0 100% /cdrom/sol_10_305_x86/s2
/vol/dev/dsk/c1t1d0/sol_10_305_x86/s0
363852 353448 0 100% /cdrom/sol_10_305_x86/s0

1. If you are using the DVD, insert it into the DVD drive. Either let vold mount the partitions, or mount
them manually. In either case, cd to the s2/Solaris_10/Tools/Boot directory and run du -sk:
4.You will not be able to read the root file system off of the CD on a Solaris on SPARC system because the UFS file system on
the CD is stored in little endian format and SPARC systems use big endian. This endian difference is the same reason that the
last five slices of a Solaris on SPARC CD on a Solaris on x86 system are not visible.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
11-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

# cd /cdrom/cdrom0/s2/Solaris_10/Tools/Boot
# du -sk .
347205 .

2. Once you know the size of the miniroot off the CD or DVD, add about 5% to this for file system
overhead. If you plan to add patches or packages to the miniroot, considering adding more than 5%.
Using this size estimate, create a UFS file system image via mkfile, lofiadm, and newfs, then
mount it. In this section, the DVD miniroot is used as an example.
3. Create an empty file of size 364565K (347205+5%).
# mkfile 364565k /var/tmp/my.miniroot

4. Map the file to a block device via the lofi driver.

# lofiadm -a /var/tmp/my.miniroot
/dev/lofi/1

5. Create a file system on the character device (notice the use of rlofi instead of lofi).
# newfs -i 8192 -m 1 /dev/rlofi/1
newfs: construct a new file system /dev/rlofi/1: (y/n)? y
/dev/rlofi/1: 729000 sectors in 1215 cylinders of 1 tracks, 600 sectors
356.0MB in 76 cyl groups (16 c/g, 4.69MB/g, 576 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
32, 9632, 19232, 28832, 38432, 48032, 57632, 67232, 76832, 86432,
633632, 643232, 652832, 662432, 672032, 681632, 691232, 700832, 710432,
720032,

6. Mount the block device.

# mount /dev/lofi/1 /mnt
# df -k /mnt
Filesystem kbytes used avail capacity Mounted on
/dev/lofi/1 357794 1041 353176 1% /mnt

7. Once the file system is mounted, copy a root image into it. The following example commands assume
that vold is running and the CD/DVD is mapped as /cdrom/cdrom0.
# cd /cdrom/cdrom0/s0 #(for CD only)

OR
# cd /cdrom/cdrom0/s2/Solaris_10/Tools/Boot #(CD or DVD)
# find . -depth -print | cpio -pdm /mnt
820112 blocks

At this point, you can make changes to the file system by modifying files under the /mnt mount point.
Some of the more useful changes include installing packages on top of this root file system via
pkgadd -R /mnt, or updating Solaris patches on it via patchadd -C /mnt. Ensure that the
updates you want to make will fit in the file system that you have created and mounted. If more space is
needed, add it to the mkfile size described previously. Because the CD consists of a standard
ISO9660 file system plus this UFS file system, make sure that the size of the miniroot plus the size of
the ISO image does not exceed what can be put on a CD (~650MB) or DVD (~4.7GB).

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
12-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

8. After completing modifications to the file system, umount the file system and delete the lofi device.
This file will later be used to append to the ISO file.
# umount /mnt
# lofiadm -d /dev/lofi/1

The result of these steps is a file representing a valid Solaris on x86 root file system with the changes you
have made.

Extracting Boot Files

Before creating the combined ISO and UFS image of the CD, you still need valid copies of the mboot,
pboot, and bootblk from the Solaris on x86 CD. To generate these files:

1. Turn off the Solaris Volume Manager:

# /etc/init.d/volmgt stop

2. Insert the Solaris for x86 CD into the CDROM drive of a system running Solaris on x86.
3. Combine mboot and pboot into a single file called mboot+pboot.cd.
# dd if=/dev/dsk/c1t1d0p0 of=mboot+pboot.cd bs=512 count=2

4. Save the Solaris on x86 bootblk into a file named bootblk.cd.

dd if=/dev/dsk/c1t1d0p0 of=bootblk.cd bs=512 iseek=4 count=60

The bootblk can also be obtained by copying the following file:

cdrom/cdrom0/s0/usr/platform/i86pc/lib/fs/ufs/bootblk

from the CD's miniroot. This approach assumes that vold is running and is using /cdrom/cdrom0 as
the base for mounting the CD.
Alternatively, with the Solaris system DVD, you can manually mount the DVD and retrieve the following
file:
Solaris_10/Tools/Boot/usr/platform/i86pc/lib/fs/ufs/bootblk

The advantage of this approach is that it works in operating systems that are unable to read a UFS off
of a DVD. However, this will work only from the DVD on non-Solaris operating systems, because the
Solaris_10/Tools/Boot directory on a CD is just a symbolic link to the s0 device (which will exist
only when running vold in Solaris).

Step 3: Create the Boot Files

The next step is to create the boot files that mkisofs will use to build the Solaris on x86 image file. Note
that copies of the boot files are used so that they are not corrupted by potential mistakes.

1. Copy the mboot+pboot.cd file to a file named .bootimage in the root directory for the ISO file
system:
# cp mboot+pboot.cd /tmp/isodir/.bootimage

2. Create the generic boot file for mkisofs by copying mboot+pboot.cd to a file named genboot,
place a 1K gap in the file (the dd command below adds a gap consisting of 1024 zeros), and then
append the Solaris bootblk:
# cp mboot+pboot.cd genboot
# dd if=/dev/zero bs=1024 count=1 >> genboot

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
13-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

# cat bootblk.cd >> genboot

Step 4: Create the Composite ISO CD Image

Using mkisofs with the -sunx86-boot option, create the composite ISO image file.

# mkisofs -r -no-emul-boot \
-b .bootimage \
-c .catalog \
-G genboot \
-o composite.iso \
-sunx86-boot /var/tmp/my.miniroot \
/tmp/isodir/

The mkisofs command will build a composite ISO image that contains the fdisk partition table and
Solaris system VTOC based on the sizes of the ISO directory and the miniroot. It will also create the El
Torito boot records required to boot the CD. The result is a combined image file named composite.iso,
which can be burned as an ISO image to the CD. This CD will be a bootable Solaris on x86 CD and will
mount the miniroot partition as its root file system.

Burning the Image

This ISO image can be burned using any software that is capable of taking a straight ISO image and
burning it to CD. The following command can be used in Solaris to burn the image, regardless of whether it
is a CD or DVD:

# cdrw -i -d <device name> composite.iso

Initializing device...done.
Writing track 1...done.
Finalizing (Can take several minutes)...done.

where <device name> is the device displayed from the output of cdrw -l.

Conclusion
There are multiple ways to achieve the same result. Parts of the process in this article can be adapted to
suit an individual user’s preferences. The real trick is to create the composite image. Before the sunx86-
boot option was included in mkisofs, users needed to write a program to create the composite image
from an ISO image and a miniroot.

You might want to use other mkisofs options, such as providing a volume name, Joliet support, and so
on. Refer to the mkisofs manual page for more information.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
14-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

References and Related Sources

• El Torito Bootable CD-ROM Format Specification Version 1.0. Phoenix Technologies Inc.,
January 25, 1995
http://www.phoenix.com/NR/rdonlyres/98D3219C-9CC9-4DF5-B496-A286D893E36A/0/specscdrom.pdf

• Performing Network Installations Without a Local Boot Server, Howard, John S. (Sun BluePrints
Online—May 2004).
http://www.sun.com/blueprints/0504/817-7288.pdf

• Building a Bootable DVD to Deploy a Solaris Flash Archive, Howard, John S. (Sun BluePrints Online—
April 2004).
http://www.sun.com/blueprints/0404/817-6991.pdf

• Customizing JumpStart Framework for Installation and Recovery, Howard, John S., and Noordergraaf,
Alex (Sun BluePrints Online—August 2002).
http://www.sun.com/blueprints/0802/816-7587-10.pdf

• mkisofs(1) Manual page

• lofiadm(1M) Manual page
http://docs.sun.com/app/docs/doc/816-0211/6m6nc66ue?a=view

• fdisk partition types

http://www.win.tue.nl/~aeb/partitions/partition_types-1.html

About the Authors

John Cecere
John started his career in computers with the United States Air Force, where he worked on Sperry Univac
mainframes. He took this experience to the civilian sector, where he perform similar job functions at Bell
Communications Research. There he first encountered Unix, and he went on to be a system administrator
for five years. He joined Sun in 1997 as a System Support Engineer and subsequently a Regional SSE.
He is currently involved in several projects writing internal tools for Sun Services.

Dana Fagerstrom
Dana Fagerstrom has been on the Service end of Sun's products for the past eight years, where he has
been supporting the US Telcos. Dana has a diverse background that spans system administration,
software development, and program management. He started at Bell Labs, moved on to Bellcore (now
Telecordia), and then to Sun. He has a MS in Computer Science from The Stevens Institute of Technology.

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005
15-Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms Sun Microsystems, Inc.

Ordering Sun Documents

The SunDocsSM program provides more than 250 manuals from Sun Microsystems, Inc. If you live in the
United States, Canada, Europe, or Japan, you can purchase documentation sets or individual manuals
through this program.

Accessing Sun Documentation Online

The docs.sun.com web site enables you to access Sun technical documentation online. You can browse
the docs.sun.com archive or search for a specific book title or subject at http://docs.sun.com/.

To reference Sun BluePrints OnLine articles, visit the Sun BluePrints OnLine Web site at:
http://www.sun.com/blueprints/online.html

Creating a Customized Boot CD/DVD for the Solaris™ Operating System for x86 Platforms — December 2005